Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 12

curing Related Abstracts

12 Effect of Mineral Additives on Improving the Geotechnical Properties of Soils in Chief

Authors: Rabah Younes

Abstract:

The reduction of available land resources and the increased cout associated with the use of high quality materials have led to the need for local soils to be used in geotechnical construction, however; poor engineering properties of these soils pose difficulties for constructions project and need to be stabilized to improve their properties in other works unsuitable soils with low bearing capacity , high plasticity coupled with high instability are frequently encountered hence, there is a need to improve the physical and mechanical characteristics of these soils to make theme more suitable for construction this can be done by using different mechanical and chemical methods clayey soil stabilization has been practiced for sometime but mixing additives, such us cement, lime and fly ash to the soil to increase its strength.

Keywords: Soil Stabilization, Clay, atterberg limits, compaction, naturaln pozzolana, compressive strength shear strength, curing

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11 Effect of Mineral Additives on Improving the Geotechnical Properties of Soils in Chlef

Authors: Messaoudi Mohammed Amin

Abstract:

The reduction of available land resources and the increased cout associated with the use of hight quality materials have led to the need for local soils to be used in geotecgnical construction however, poor engineering properties of these soils pose difficulties for constructions project and need to be stabilized to improve their properties in oyher works unsuitable soils with low bearing capacity, high plasticity coupled with high insatbility are frequently encountered hense, there is a need to improve the physical and mechanical charateristics of these soils to make theme more suitable for construction this can be done by using different mechanical and chemical methods clayey soil stabilization has been practiced for quite sometime bu mixing additives, such us cement, lime and fly ash to the soil to increase its strength. The aim of this project is to study the effect of using lime, natural pozzolana or combination of both on the geotecgnical cherateristics of clayey soil. Test specimen were subjected to atterberg limits test, compaction test, box shear test and uncomfined compression test Lime or natural pozzolana was added to clayey soil at rangs of 0-8% and 0-20% respectively. In addition combinations of lime –natural pozzolana were added to clayey soil at the same ranges specimen were cured for 1-7, and 28 days after which they were tested for uncofined compression tests. Based on the experimental results, it was concluded that an important decrease of plasticity index was observed for thr samples stabilized with the combinition lime-natural pozzolana in addition, the use of the combination lime-natural pozzolana modifies the clayey soil classification according to casagrand plasiticity chart. Moreover, based on the favourable results of shear and compression strength obtained, it can be concluded that clayey soil can be successfuly stabilized by combined action of lime and natural pozzolana also this combination showed an appreciable improvement of the shear parameters. Finally, since natural pozzolana is much cheaper than lime ,the addition of natural pozzolana in lime soil mix may particulary become attractive and can result in cost reduction of construction.

Keywords: Soil Stabilization, Clay, atterberg limits, compaction, natural pozzolana, compressive strength shear strength, curing

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10 Relation between Properties of Internally Cured Concrete and Water Cement Ratio

Authors: T. Manzur, S. Iffat, M. A. Noor

Abstract:

In this paper, relationship between different properties of IC concrete and water cement ratio, obtained from a comprehensive experiment conducted on IC using local materials (Burnt clay chips- BC) is presented. In addition, saturated SAP was used as an IC material in some cases. Relationships have been developed through regression analysis. The focus of this analysis is on developing relationship between a dependent variable and an independent variable. Different percent replacements of BC and water cement ratios were used. Compressive strength, modulus of elasticity, water permeability and chloride permeability were tested and variations of these parameters were analyzed with respect to water cement ratio.

Keywords: Concrete, compressive strength, aggregate, lightweight, curing, internal curing, superabsorbent polymer

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9 Towards Sustainable Concrete: Maturity Method to Evaluate the Effect of Curing Conditions on the Strength Development in Concrete Structures under Kuwait Environmental Conditions

Authors: J. Chakkamalayath, A. Al-Aibani, F. Al-Fahad

Abstract:

Conventional methods of determination of concrete strength under controlled laboratory conditions will not accurately represent the actual strength of concrete developed under site curing conditions. This difference in strength measurement will be more in the extreme environment in Kuwait as it is characterized by hot marine environment with normal temperature in summer exceeding 50°C accompanied by dry wind in desert areas and salt laden wind on marine and on shore areas. Therefore, it is required to have test methods to measure the in-place properties of concrete for quality assurance and for the development of durable concrete structures. The maturity method, which defines the strength of a given concrete mix as a function of its age and temperature history, is an approach for quality control for the production of sustainable and durable concrete structures. The unique harsh environmental conditions in Kuwait make it impractical to adopt experiences and empirical equations developed from the maturity methods in other countries. Concrete curing, especially in the early age plays an important role in developing and improving the strength of the structure. This paper investigates the use of maturity method to assess the effectiveness of three different types of curing methods on the compressive and flexural strength development of one high strength concrete mix of 60 MPa produced with silica fume. This maturity approach was used to predict accurately, the concrete compressive and flexural strength at later ages under different curing conditions. Maturity curves were developed for compressive and flexure strengths for a commonly used concrete mix in Kuwait, which was cured using three different curing conditions, including water curing, external spray coating and the use of internal curing compound during concrete mixing. It was observed that the maturity curve developed for the same mix depends on the type of curing conditions. It can be used to predict the concrete strength under different exposure and curing conditions. This study showed that concrete curing with external spray curing method cannot be recommended to use as it failed to aid concrete in reaching accepted values of strength, especially for flexural strength. Using internal curing compound lead to accepted levels of strength when compared with water cuing. Utilization of the developed maturity curves will help contactors and engineers to determine the in-place concrete strength at any time, and under different curing conditions. This will help in deciding the appropriate time to remove the formwork. The reduction in construction time and cost has positive impacts towards sustainable construction.

Keywords: Durability, Maturity, Strength, curing

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8 Material Concepts and Processing Methods for Electrical Insulation

Authors: R. Sekula

Abstract:

Epoxy composites are broadly used as an electrical insulation for the high voltage applications since only such materials can fulfill particular mechanical, thermal, and dielectric requirements. However, properties of the final product are strongly dependent on proper manufacturing process with minimized material failures, as too large shrinkage, voids and cracks. Therefore, application of proper materials (epoxy, hardener, and filler) and process parameters (mold temperature, filling time, filling velocity, initial temperature of internal parts, gelation time), as well as design and geometric parameters are essential features for final quality of the produced components. In this paper, an approach for three-dimensional modeling of all molding stages, namely filling, curing and post-curing is presented. The reactive molding simulation tool is based on a commercial CFD package, and include dedicated models describing viscosity and reaction kinetics that have been successfully implemented to simulate the reactive nature of the system with exothermic effect. Also a dedicated simulation procedure for stress and shrinkage calculations, as well as simulation results are presented in the paper. Second part of the paper is dedicated to recent developments on formulations of functional composites for electrical insulation applications, focusing on thermally conductive materials. Concepts based on filler modifications for epoxy electrical composites have been presented, including the results of the obtained properties. Finally, having in mind tough environmental regulations, in addition to current process and design aspects, an approach for product re-design has been presented focusing on replacement of epoxy material with the thermoplastic one. Such “design-for-recycling” method is one of new directions associated with development of new material and processing concepts of electrical products and brings a lot of additional research challenges. For that, one of the successful products has been presented to illustrate the presented methodology.

Keywords: Recycling, Numerical Simulations, curing, epoxy insulation

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7 Hysteresis Behaviour of Mass Concrete Mixed with Plastic Fibre under Compression

Authors: A. A. Okeola, T. I. Sijuade

Abstract:

Unreinforced concrete is a comparatively brittle substance when exposed to tensile stresses, the required tensile strength is provided by the introduction of steel which is used as reinforcement. The strength of concrete may be improved tremendously by the addition of fibre. This study focused on investigating the compressive strength of mass concrete mixed with different percentage of plastic fibre. Twelve samples of concrete cubes with varied percentage of plastic fibre at 7, 14 and 28 days of water submerged curing were tested under compression loading. The result shows that the compressive strength of plastic fibre reinforced concrete increased with rise in curing age. The strength increases for all percentage dosage of fibre used for the concrete. The density of the Plastic Fibre Reinforced Concrete (PFRC) also increases with curing age, which implies that during curing, concrete absorbs water which aids its hydration. The least compressive strength obtained with the introduction of plastic fibre is more than the targeted 20 N/mm2 recommended for construction work showing that PFRC can be used where significant loading is expected.

Keywords: Concrete, Density, compressive strength, curing, plastic fibre

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6 Adverse Curing Conditions and Performance of Concrete: Bangladesh Perspective

Authors: T. Manzur

Abstract:

Concrete is the predominant construction material in Bangladesh. In large projects, stringent quality control procedures are usually followed under the supervision of experienced engineers and skilled labors. However, in the case of small projects and particularly at distant locations from major cities, proper quality control is often an issue. It has been found from experience that such quality related issues mainly arise from inappropriate proportioning of concrete mixes and improper curing conditions. In most cases external curing method is followed which requires supply of adequate quantity of water along with proper protection against evaporation. Often these conditions are found missing in the general construction sites and eventually lead to production of weaker concrete both in terms of strength and durability. In this study, an attempt has been made to investigate the performance of general concreting works of the country when subjected to several adverse curing conditions that are quite common in various small to medium construction sites. A total of six different types of adverse curing conditions were simulated in the laboratory and samples were kept under those conditions for several days. A set of samples was also submerged in normal curing condition having proper supply of curing water. Performance of concrete was evaluated in terms of compressive strength, tensile strength, chloride permeability and drying shrinkage. About 37% and 25% reduction in 28-day compressive and tensile strength were observed respectively, for samples subjected to most adverse curing condition as compared to the samples under normal curing conditions. Normal curing concrete exhibited moderate permeability (close to low permeability) whereas concrete under adverse curing conditions showed very high permeability values. Similar results were also obtained for shrinkage tests. This study, thus, will assist concerned engineers and supervisors to understand the importance of quality assurance during the curing period of concrete.

Keywords: Concrete, Permeability, Tensile Strength, compressive strength, curing, adverse, drying shrinkage

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5 Modelling the Effects of External Factors Affecting Concrete Carbonation

Authors: Abhishek Mangal, Kunal Tongaria, S. Mandal, Devendra Mohan

Abstract:

Carbonation of reinforced concrete structures has emerged as one of the major challenges for Civil engineers across the world. With increasing emissions from various activities, carbon dioxide concentration in the atmosphere has been eve rising, enhancing its penetration in porous concrete, reaching steel bars and ultimately leading to premature failure. Several literatures have been published dealing with the various interdependent variables related to carbonation. However, with innumerable variability a generalization of these data proves to be a troublesome task. This paper looks into this carbonation anomaly in concrete structures caused by various external variables such as relative humidity, concentration of CO2, curing period and ambient temperature. Significant discussions and comparisons have been presented on the basis of various studies conducted with an aim to predict the depth of carbonation as a function of these multidimensional parameters using various numerical and statistical modelling techniques.

Keywords: carbonation, relative humidity, curing, exposure conditions

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4 Studies on Partial Replacement of Cement by Rice Husk Ash under Sodium Phosphate Medium

Authors: Chandan Kumar Patnaikuni, Dharmana Pradeep, N. V. S. Venugopal

Abstract:

Rice Husk Ash (RHA) is a green product contains carbon and also loaded with silica. For the development of durability and strength of any concrete, curing phenomenon shall be very important. In this communication, we reported the exposure of partial replacement of cement with RHA at different percentages of 0%, 5%, 7.5%, 10%, 12.5% and 15% by weight under sodium phosphate curing atmosphere. The mix is designed for M40 grade concrete with the proportions of 1:2.2:3.72. The tests conducted on concrete was a compressive strength, and the specimens were cured in normal water & exposed to the chemical solution for 7, 28 & 56 days. For chemical curing 0.5% & 1% concentrated sodium phosphates were used and were compared with normal concrete strength results. The strength of specimens of 1% sodium phosphate exposure showed that the compressive strength decreased with increase in RHA percentages.

Keywords: compressive strength, rice husk ash, curing, sodium phosphate

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3 Investigating the Mechanical Properties of Geopolymer Concrete Containing Microencapsulated Phase Change Materials

Authors: Vinh Duy Cao, Anna M. Szczotok, Anna-Lena Kjøniksen, Shima Pilehvar

Abstract:

Micro encapsulated phase change materials (MPCM) may be utilized to increase the energy efficiency of buildings by the addition of MPCM to concrete structures. However, addition of MPCM to Portland cement concrete is known to reduce the compressive strength of the concrete. Accordingly, it is interesting to also examine the effect of adding MPCM to geopolymer concrete. Geopolymer binder is synthesized by mixing aluminosilicate materials in amorphous form with a strong alkali activator, and have a much lower CO2 footprint than Portland cement concrete. In this study, the mechanical properties of fly ash-based geopolymer concrete with different types and contents of MPCM were investigated at different curing temperatures. The aim was to find the optimum amount of MPCM which still maintain the workability and compressive strength at an acceptable level. The results revealed that both workability and compressive strength of geopolymer concrete decrease after adding MPCM. Also, the percentage of strength reduction can be variable by different types of MPCM.

Keywords: Concrete, Geopolymer, compressive strength, curing, micro-encapsulated PCM

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2 Quality Characteristics of Cured Dried Camel Meat Formulated with Different Medicinal Plants as Natural Preservatives

Authors: H. S. Aljabeili, E. A. Abd El-Hady, M. M. Abd El-Razik, M. Abd Elgadir

Abstract:

The aim of the study is determining the quality characteristics of produced curing and dried camel meat contained some medicinal plants of thyme, rosemary, clove and ginger as natural preservatives. Camel meat samples were sliced and divided into five batches, one batch recorded as control sample was treated by the curing mixture (2.5%) contained the following ingredients: black pepper 1 gm, cumin 0.4 gm, spices mixture 0.5 gm, dried onion 3 gm, dried garlic 0.5 gm and salt 2 gm. To evaluate the effect of different natural preservatives sources of thyme, rosemary, clove and ginger, 3.0% of the aforementioned natural preservatives was mixed with the aforementioned curing mixture and used for curing the four batches of sliced camel meat. After curing process, cured sliced camel meat (control and treated with the natural preservatives) were conducting to drying process at 35 ± 3 °C for 36 h in a drying cabinet. The quality characteristics of prepared dried camel meat were evaluated such as chemical composition, microbiological characteristics and sensory characteristics. Based on the microbiological and sensory characteristics, it could be suggested that the selected medicinal plants specially thyme and rosemary could be used as natural preservatives for preparing semi dry camel meat without negative effects.

Keywords: Medicinal Plants, Quality Characteristics, Natural Preservatives, curing, dried camel meat

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1 Utilization of Fly Ash Amended Sewage Sludge as Sustainable Building Material

Authors: Manish Kumar, KALING TAKI, ROHIT GAHLOT

Abstract:

Disposal of Sewage Sludge (SS) is a big issue especially in developing nation like India, where there is no control in the dynamicity of SS produced. The present research work demonstrates the potential application of SS amended with varying percentage (0-100%) of Fly Ash (FA) for brick manufacturing as an alternative of SS management. SS samples were collected from Jaspur sewage treatment plant (Ahmedabad, India) and subjected to different preconditioning treatments: (i) atmospheric drying (ii) pulverization (iii) heat treatment in oven (110°C, moisture removal) and muffle furnace (440°C, organic content removal). Geotechnical parameters of the SS were obtained as liquid limit (52%), plastic limit (24%), shrinkage limit (10%), plasticity index (28%), differential free swell index (DFSI, 47%), silt (68%), clay (27%), organic content (5%), optimum moisture content (OMC, 20%), maximum dry density (MDD, 1.55gm/cc), specific gravity (2.66), swell pressure (57kPa) and unconfined compressive strength (UCS, 207kPa). For FA liquid limit, plastic limit and specific gravity was 44%, 0% and 2.2 respectively. Initially, for brick casting pulverized SS sample was heat treated in a muffle furnace around 440℃ (5 hours) for removal of organic matter. Later, mixing of SS, FA and water by weight ratio was done at OMC. 7*7*7 cm3 sample mold was used for casting bricks at MDD. Brick samples were then first dried in room temperature for 24 hours, then in oven at 100℃ (24 hours) and finally firing in muffle furnace for 1000℃ (10 hours). The fired brick samples were then cured for 3 days according to Indian Standards (IS) common burnt clay building bricks- specification (5th revision). The Compressive strength of brick samples (0, 10, 20, 30, 40, 50 ,60, 70, 80, 90, 100%) of FA were 0.45, 0.76, 1.89, 1.83, 4.02, 3.74, 3.42, 3.19, 2.87, 0.78 and 4.95MPa when evaluated through compressive testing machine (CTM) for a stress rate of 14MPa/min. The highest strength was obtained at 40% FA mixture i.e. 4.02MPa which is much higher than the pure SS brick sample. According to IS 1077: 1992 this combination gives strength more than 3.5 MPa and can be utilized as common building bricks. The loss in weight after firing was much higher than the oven treatment, this might be due to degradation temperature higher than 100℃. The thermal conductivity of the fired brick was obtained as 0.44Wm-1K-1, indicating better insulation properties than other reported studies. TCLP (Toxicity characteristic leaching procedure) test of Cr, Cu, Co, Fe and Ni in raw SS was found as 69, 70, 21, 39502 and 47 mg/kg. The study positively concludes that SS and FA at optimum ratio can be utilized as common building bricks such as partitioning wall and other small strength requirement works. The uniqueness of the work is it emphasizes on utilization of FA for stabilizing SS as construction material as a replacement of natural clay as reported in existing studies.

Keywords: fly ash, Sewage Sludge, compressive strength, curing

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